PHOENIX — State lawmakers took the first steps Tuesday to cut down on so-called “dark money’’ in political campaigns, but with no clear indication if their plan will work, or whether it’s even legal.

Legislation approved by the Senate Elections Committee requires all campaign commercials, literature and similar materials to include the names of the three largest contributors. Sen. Michele Reagan, R-Scottsdale, said it’s unacceptable that people can spend large amounts of money to influence elections and remain hidden.

On paper, the vote for SCR 1003 was unanimous. But several GOP legislators, after hearing from lobbyists, said they fear the measure creates unnecessary hurdles.

And Sen. Kimberly Yee, R-Phoenix, openly worried requiring people to get out from behind the committees they create to affect elections might chill their First Amendment rights to speak freely.

That contention drew derision from Reagan. She said Arizona has moved for years in the direction of greater disclosure.

“Then wouldn’t spending have gone down?” she asked. “But it hasn’t.”

And she lashed out at the lobbyist and special interests who are on record in opposition, ranging from the Arizona Chamber of Commerce and Industry to the state AFL-CIO.

“Their clients do not want you to see what they’re doing,’’ Reagan said.

The problem is there has been a proliferation of independent campaign committees, especially in the wake of a 2010 U.S. Supreme Court ruling allowing corporations to influence elections. But any campaign reports filed — and not all of them do — list their donors as yet other organizations.

Secretary of State Ken Bennett said it doesn’t stop there, with those organizations listing still other groups with nebulous names as contributors. Bennett compared the system to Russian nesting dolls.

“We’re seeing problems all over the country and in our state of people, the public, not being able to tell who is trying to influence their vote,” he told lawmakers, which Bennett told legislators should concern them.

But problems remain for the law.

One is a state court ruling that concluded not all TV commercials and mailings that mention candidates are considered efforts to influence an election. The judge said they can fit within the definition of “issue-oriented speech,” which is not covered by campaign finance laws, even if they run right before the election and say negative things about a candidate.

Reagan said she hopes the language of what the law covers, known as “express advocacy,” can be made broad enough to ensure that some “hit pieces” do not escape disclosure requirements.

The bigger issue may prove legal. Attorney Mike Liburdi told lawmakers they have to recognize there are constitutional rights at issue. And he argued individuals are free to exercise their First Amendment rights anonymously.

“Disclosure of some of these speakers may result in a chilling effect,” Liburdi said. “And this chilling effect could suppress speech.”

He represents the Arizona Victory Alliance, which spent more than $475,000 in independent expenditures last election to elect Republicans and defeat Democrats. Much of that cash came from other political action committees and organizations.